The invention relates to processes for applying magnetic medium material to a disk.
In the past, fluid carrying magnetic medium material has typically been applied while the disk is rotated at low speed, with the speed of the disk then being increased during a high speed spin-out step to spin excess medium material off of the disk by means of centrifugal force. See, for example, U.S. Pat. Nos. 4,353,937; 4,133,911; and 3,198,657. The disk was then processed through a magnetic orientation step and a drying step before being baked and polished. The polishing was done both to improve the surface finish of the disk and to reduce the thickness of the media film applied to the disk.
Since the fluid carrying magnetic medium material was applied to the disk at a very low speed, the fluid would undergo very rapid viscosity changes prior to the high speed spin-out step which resulted in a relatively thick film of medium material ultimately adhering to the disk.
The process also provided ample opportunity for air-borne particles to settle on the disk and later cause radially directed runs to form during the high speed spin-out step as the fluid would attempt to flow around the particle as it was spun radially off of the disk. In addition, circumferentially directed scratches were caused during the polishing operation where a particle was picked up by the polishing tape. Furthermore, coating flaws known as "wraparounds" have occurred wherein the fluid flows from one side of the disk around the edge to the other side of the disk.